What causes a Unity editor GUILayout ArgumentException?

Your custom editor code changed the number of GUILayout controls between the layout and repaint passes — an early return, a conditional control, or a mismatched Begin/End — so Unity's immediate-mode GUI gets confused.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix “ArgumentException: Getting control's position in a group” in Unity

Quick answer: Make sure your editor GUI issues the same controls every pass, balance every BeginHorizontal/Vertical with an End, and avoid returning early or changing control counts mid-OnGUI.

This ArgumentException comes from custom editor or EditorWindow code where the GUI control count differs between passes. Keeping it consistent fixes it. Here is how.

How to fix it

1. Issue the same controls every pass

Unity's immediate GUI runs layout and repaint passes that must see the same controls. A control behind a condition that changes between passes, or an early return, breaks the count. Keep the structure stable.

2. Balance Begin and End

Every BeginHorizontal, BeginVertical, and BeginArea needs a matching End on every path. An unbalanced pair (especially inside a conditional) triggers this exception. Audit them.

3. Avoid changing counts mid-GUI

Do not add or remove controls based on state that changes within OnGUI, and do not return early between Begin and End. Compute conditions before the GUI block so the control set is fixed for the frame.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.